Expansion, adiabatic throttled

Solid carbon dioxide can be manufactured by expanding liquid CO through an adiabatic throttling valve. If CO2 is available for the process as a saturated liquid at 800 psia and the expansion reduces the pressure to 14.7 psia, how many pounds of solid carbon dioxide are produced per pound of liquid CO2 ... 

Steam Rate Enthalpy data can be obtained from Mollier diagrams or from steam tables (see Sec. 2), from which the theoretical steam rate can be calculated. For example, a throttle inlet condition of 4137 kPa (600 psig) and 399° C (750° F) gives an enthalpy of 3.2 MJ/kg (1380 Btu/lb), and if the end point is at 348 kPa (50 psig), then adiabatic expansion is to 2.69 MJ/kg (1157 Btu/lb). This gives 0.52 MJ/kg (223 Btu/lb) available, and the theoretical steam rate is calculated from the Btu equivalent per Idlowatthour or horsepower-hour ... 

The mechanism of hquid phase (fog) formation behind a throttle placed in a supply pipe before a separator is based on the process of adiabatic expansion of the gas mixture. In this process, the volume of the mixture increases and the pressure and temperature of the vapor decrease, since the work of expansion is done by the internal energy of the gas. The saturated vapor pressure is reduced by the temperature decrease and this results in increased vapor supersaturation. The degree of supersaturation, s, expresses the ratio of the vapor pressure in the gas, pv> to the saturated vapor pressure, pvoo, above a flat surface of the same liquid ... 

A way to achieve cooling and supersaturation of mixtures is adiabatic expansion of a gas due to a throttle effect. In the realm of gas and gas-condensate fields, low-temperature separation (LTS) schemes are used, which include a combination of technological processes directed towards cooling of the production from wells to the requisite temperatures to facilitate separation. The LTS scheme is applied after the gas has been purged of most of the mass of liquid phase in the entrance separator, practically without changes of pressure and temperature. LTS is subsequently applied to condense water vapor and heavy hydrocarbons (HC). LTS entails the following processes. 

Throttling and adiabatic expansion of gas in turbo-expanders occur as a result of gas flow in pipes and channels of variable cross-section. To determine the temperature, pressure, and degree of supersaturation of a mixture in these devices it is necessary to carry out appropriate gas-dynamic calculations. An approach to performing such calculations, based on ref. [5], is outlined below. 

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